I banged my knee a few weeks ago and it just didn’t get back to normal so my wife took me to the doctor to figure out what to do. As part of the exam they made X-rays of the joint to find out if something was loose. It got me to thinking about how we create photographs.
As much as we talk about using light to create our images the process is actually indirect. We capture the reflection of light off our subjects, not the light directly. It’s only on rare occasions like fireworks, sunsets or nighttime shots of city lights that we rely on the direct capture of light as a subject. A direct photograph of light usually is just a blob of white with no detail – what’s the interest in that?
But X-rays by their nature make images by the direct capture of light. Sure, it’s the dark areas that are of interest to us, but these are shadows blocking the light from hitting the film (or sensor mostly now) so in a sense the image is truly created by direct capture of light.
This is useful because the energy of X-rays (a form of light we can’t see) allow them to penetrate objects we have a hard time seeing the inside of and that helps doctors, engineers and scientists view elements without taking the subject apart. The light we use for photography isn’t energetic enough to penetrate most of our subjects; as a result we usually don’t wonder what’s inside of them. Still, even though the frequency of visible light isn’t energetic enough to penetrate that doesn’t mean we can’t use it to display the inside of subjects. Crank up the intensity of the light and shine it through a thin enough subject, and it will reveal what’s inside.
For fun I set up my most powerful flash, put my macro lens on the camera and set up a rig where I could shine the flash’s light through some subjects. None of these revealed elements are invisible to us; it’s just most people don’t hold them up to a bright enough light to see some of their internal elements. My subjects were just household items but now I’m keeping my eye open for other, more novel subjects for visible “X-rays.” Got any ideas of where to look?